Severe Acute Respiratory Syndrome (SARS) is an emerging infectious illness with a tendency for rapid spread from person to person (MMWR Morb Mortal Wkly Rep, 52 (12): 255-6, 2003; MMWR Morb Mortal Wkly Rep, 52 (12): 241-6, 248, 2003; Lee N et al., N Engl J Med, 348(20):1986-94, 2003; Poutanen S M et al., N Engl J Med, 348(20):1995-2005, 2003). A newly identified coronavirus is now established as the etiologic agent (Drosten C et al., N Engl J Med, 348(20):1967-76, 2003; Ksiazek T G et al., N Engl J Med, N Engl J Med, 348(20):1953-66, 2003). Coronaviruses have characteristic surface peplomer spikes formed by oligomers of the surface S-glycoprotein. The S-glycoproteins are believed to bind receptors on target cells. The S-proteins are the principal targets for neutralizing antibodies (Saif L J, Vet Microbiol, 37 (3-4): 285-97, 1993). The protective efficacy of humoral immunity has been demonstrated in several animal models of coronavirus disease (e.g., avian infectious bronchitis virus disease and respiratory bovine coronavirus disease) (Lin X et al., Clin Diagn Lab Immunol, 8 (2): 357-62, 2001; Mondal S P, and Naqi S A, Vet Immunol Immunopathol, 79 (1-2): 31-40, 2001; Wang X et al., Avian Dis, 46 (4): 831-8, 2002.18).
The recently published sequence of the human SARS corona virus (human SARS-CoV) reveals that it represents a new strain (Drosten C et al., N Engl J Med, 348(20):1967-76, 2003; Ksiazek T G et al., N Engl J Med, 348(20):1953-66, 2003). While it is seroreactive with some antisera and monoclonal antibodies to group 1 coronaviruses, it appears to be best classified as a fourth serogroup given its sequence divergence from other strains. Neutralization with available antibodies has not been reported. With the rapid spread of the SARS epidemic and a mortality rate of 5%, it is crucial to develop therapeutic and prophylactic agents. The most severe clinical outcomes of this infection have been associated with prolonged viremia (Drosten C et al., N Engl J Med, 348(20):1967-76, 2003).
Laboratory analyses of convalescent serum samples from individuals with SARS have shown high levels of specific reactivity with infected cells and conversion from negative to positive reactivity or diagnostic rises in the indirect fluorescence antibody test (Ksiazek T G et al., N Engl J Med, 348(20):1953-66, 2003). In contrast, sera from United States blood donors and persons with known HCV 229E or OC43 infection were negative for antibodies to this novel coronavirus. These results indicate that this virus has not been widely circulated in human populations (Ksiazek T G et al., N Engl J Med, 348(20):1953-66, 2003).